1. Field of the Invention
The invention relates to a ratchet mechanism for telescope devices on toy vehicles, in particular for telescope supports of crane jibs of toy crane trucks, comprising a manually drivable driving gearwheel rotatably positioned on a telescope base body, a rack-type row of teeth engaging with the driving gearwheel and disposed on a telescope arm which is lodged for longitudinal displacement in the telescope base body, and a pawl being in ratcheting engagement with a tooth gap between two teeth of the driving gearwheel for the telescopic arm to be fixed in different positions of displacement on the telescope base body.
2. Background Art
Ratchet mechanisms of the generic type are very often used in toy vehicles for the most various telescope devices. The use in telescopable crane jibs as such or in laterally extractable supports for the improvement of the stability of a crane truck is to be mentioned in addition to the example mentioned.
In all these possible applications the ratchet mechanism has different purposes, namely, on the one hand, to ensure the drive of the extractable telescopic arm and to fix the telescopic arm in positions of displacement of grid-type sequence on the telescope base body. A mechanism of this type as conventionally used has a manually drivable driving gearwheel which engages with a rack-type row of teeth on the displaceable telescopic arm. A pawl engaging with the driving gear wheel in the way of a ratchet is provided for blocking the telescopic arm; the pawl is suitably actuated, for instance by a spring, in the direction of engagement so as to ensure the mechanism to be reliably blocked in a direction of rotation of the driving gearwheel--as a rule the direction of rotation assigned to the retraction of the telescopic arm.
In order for the telescopic arm to be able to move in the blocked direction, the pawl must be disengaged from the driving gearwheel, which may for instance be done by an externally actuatable release lever. But this causes considerable difficulties in the handling especially by children, since two actuating operations have to be performed simultaneously.
An even more important disadvantage of such constructions resides in the fact that the pawl causes the driving gearwheel and consequently the associated telescopic arm to be blocked inflexibly at least in one direction of movement. If a child tries to push in the telescopic arm inappropriately, directly forcing it in without actuating the driving gearwheel, there is the risk that the pawl breaks and the blocking effect of the ratchet mechanism gets lost, in which case the toy vehicle is as a rule no longer of any use.